A tire used on snowy roads is provided in the tread portion with a plurality of main grooves continuously extending in the tire circumferential direction, and a plurality of transverse grooves extending in the tire axial direction so as to exert on-the-snow performances such as on-the-snow traction performance and on-the-snow lateral grip performance. The on-the-snow traction performance (driving force on snowy roads) is brought about shearing force of the snow packed into the transverse grooves. The on-the-snow lateral grip performance (running stability when turning a steering wheel during running on snowy roads) is brought about frictional force caused by the circumferential component of the edges of the main grooves. To improve such on-the-snow performances is an everlasting problem for the tires used on snowy roads.